Heater apparatus



July 23, 1968 L 1 w, K|NG ET AL 3,394,251 v HEATER APPARATUS Filed May l2, 1966 JosPH M Kfm/6, Raaf/P7' f. Aasous, ,r6/rev M @Av/.s

INVENTORS United States Patent O poration of Delaware Filed May 12, 1966, Ser. No. 549,564 6 Claims. (Cl. 246-428) This invention relates to means for heating railway rails to prevent undesirable accumulations of ice or snow.

In modern railroad operations, it is necessary to prevent or remove substantial accumulations of ice or snow at rail switches and other locations on railroad rails in climates where such accumulations can occur. Otherwise, proper operation of the switches and such other portions of the rails could be impaired if not prevented, with consequent possibilities of damage or danger to rolling stock` or personnel.

Undesirable accumulations of ice and snow heretofore have been prevented or removed -by the application of heat to the rails by two general types of heating means: Gas red or electrically energized infrared heaters designed and located to direct infrared radiation at the desired location on the rail; and mechanically attached strip type, generally tubular, electrical heaters that transmit heat by conduction to the desired portions of the rail. Heaters of these types are quite expensive to install, to operate and to maintain, and are characterized by other disadvantages.

Gas or electric infrared heaters generally used are mounted a substantial distance from the area to be heated, so that their eiiiciencies are reduced according to the inverse square law.

The mechanically attached electrical strip heaters are usually attached to the rail by spaced clips or the like; as such heater expands, it usually sags or droops away from the rail between its points of attachment, so these heaters, at least when operating, are generally in contact with the rail only at those points where they are attached to the rail. Consequently, heat is transferred to the rail largely by radiation and convection, rather than by conduction; this causes inefficiency in heating. Furthermore, it is necessary to drill numerous special holes through the rail to permit the attachment of such prior mechanically attached heaters by the metal clips or other fasteners. Such clips and heaters also tend to loosen from shocks and vibrations caused by vehicles traveling on the rail; this impairs conduction of heat to the rail and can even totally disconnect the heater from the rail. Fuithermore, when, as is usually the case, such a mechanically attached electrical strip heater is mounted on the inside or gauge side of the stock rail in a switch, it is necessary to provide a specially shaped switch point that clears the heater and does not damage it; this is usually done by grinding or milling the switch point. Consequently, the strip heaters heretofore used that have been attached to the rails have been expensive to install and have not been as effective as desired.

Sometimes it is desired to mount the heater on the switch point, since this more effectively keeps ice or snow accumulations from forming on the switch point itself, which usually is unheated when not in contact with the stock rail. The generally used prior strip heaters have not lent themselves to mounting on the switch point.

An object of the present invention is the provision of an electrical strip heater that can overcome or avoid as many of the above disadvantages as is desired. Another object is the provision of an electrical strip heater that is exceptionally efficient because its heating element is mounted on and in extremely close proximity to the ICC rail so that heat can be transferred essentially entirely by conduction from the heating element to the rail at the desired location. A further object is the provision of a conduction type heater that can be installed with no special drilling of the rail on which it is mounted or, if it is installed on the stock rail between a switch point and the stock rail, that can be installed without the necessity of providing a switch point of special shape. A further object is the provision of a heater that can be readily mounted on the movable part of the rail, such as a switch point, to heat it to prevent accumulation of snow and ice.

These and other objects of the invention will become apparent from the following description of a preferred embodiment thereof, in connection with the accompanying drawings in which:

FIGURE l is a perspective of a portion of a stock rail on which is mounted a heater embodying the invention, and a portion of a switch point that is positioned adjacent the stock rail, the heater being mounted on the stock rail between the stock rail and the switch point;

F-IGURE 2 is a section along line 2 2 of FIGURE 1 and to a larger scale showing cross sections of the stock rail and the switch point, and the heater mounted on the stock rail between the switch point and the stock rail; and

FIGURE 3 is a section, to a scale considerably larger than that of FIGURE 2, showing in greater detail the heater mounted on the rail.

In the illustrated embodiment, the stock rail 1, having head 2, web 3, and base 4, on its web 3 has two strip heaters 5 and 6, connected in series through connecting means 7. Power supply leads 8 and 9 are connected to the ends of the heaters 5 and 6 to supply electrical energy from a suitable source of A.C. or D.C. power, not shown. The heater strips are mounted on the web of the stock rail 1 between the stock rail 1 and the switch point 10.

Each of the illustrated heaters 5 and 6 preferably is a commercially available strip approximately eight feet long, 11/2 wide, and approximately 0.35 thick. As shown in FIGURE 3, each strip heater comprises transversely-spaced, longitudinally-extending groups 11 of suitable electrical resistance heating Wires 12 laminated between layers of glass fiber cloth 13, the whole being impregnated with silicon rubber 14 and bonded together as one strip unit. Terminals 15 (FIGURE l) with high temperature resistant insulation are provided at either end of each strip to make possible electrical connections to adjacent heating strips or to the power supply. Depending on the amount of heating required, the heating strips that are preferably used are chosen from those rated at 1400 watts at volts; or at 1700 watts at 150 volts, or at 1400 wats at 220 volts.

Each heating strip 5 or 6 is firmly bonded by an adhesive 16 to the rail. In the illustrated embodiment, this may be accomplished by the following preferred process. The switch stops are first removed from the switch point. The web of the gauge side of the stock rail is cleaned, preferably by Sandblasting, at the location where the heater strips are to be mounted, the sandblasted area preferably being a strip at least 21/2 Wide and somewhat longer than the length of the series-connected heater strips, and located near the head 2 of the rail. By brush, roller or spray a primer suitable for a silicone rubber adhesive, such as the primer identified as SS 4004 manufactured by General Electric Company, Silicones Division, Waterford, N.Y., is applied on the cleaned area at the location on which each heater is to be applied. The primer is allowed to dry. Then a liquid silicone rubber adhesive, which when dry forms a highly adherent flexible silicone rubber layer and has high temperature and air cure characteristics, such as adhesive RTV-106 manufactured by General Electric Company, Silicones Division, Waterford, N Y., is spread on `one side of the heater strip and over the dried primer previously applied to the rail. Preferably, the adhesive is applied in a strip approximately 21/2 `wide on the cleaned area just bel-ow the head of the rail. After an eight foot section of Iadhesive has been applied, the lirst heater `strip is pressed into position in the desired position. Once in position the excess of adhesive and any entrapped air is manually pressed out from between the heater strip and the rail. The next heating strip is applied in the same manner, generally concurrently with the first heating strip. Since the adhesive is an air cure silicone rubber bonding material, it cures without further attention. There is thus provided a thin and uniform heat resistant, heat conductive bonding layer 16 that assures good transfer by conduction from the heater 5 or 6 to the rail 1, and eliminates the possibility of hot spots developing in the heater.

The lead wire on each end of each strip is cut so that approximately 3 of wire is provided. The insulation is stripped to provide approximately 3s" of exposed wire. A 3" long length of heat-shrinkable silicone tubing is then slipped over one of the two wires between two adjacent strips. A crimp connector is then used to connect the two lead wires, after which the crimp connector and joined wires are covered with the adhesive used to bond the heater to the rail. The silicone rubber tubing is then pulled up over the crimp connector and the adhesive on the crimp connector. Heat is yapplied to the silicone tubing to shrink the tubing and insure a weatherproof connection.

If it is necessary to replace the switch stops, they may be bolted to the stock rail between the heater strips, which preferably are located to insure that they miss the points where the switch stops would be used. However, it is preferable to use a modified switch stop such as that shown in FIGURE 2. This switch stop is mounted on the web 3 of the stock rail 1, and comprises a large bolt 17 that has nuts 18 and 19 threaded on the bolt on each side of the web firmly to hold the bolt in place. The head 21 of the bolt acts to stop the switch point at the proper -distance when it is moved to its closest position relative to the stock rail. Each switch stop, of course, should be located to avoid the heater strip.

The above described structure provides complete contact between each heater strip and the stock rail to insure highly uniform transfer of heat by conduction over the entire area of the heater srtip. This avoids the difficulties inherent in prior strip heaters in which the heater strips are fastened into place with metal clips and maintain contact wth the stock rail only at those points where the clip is used and in which the heater strips tend to move away from the rail between the points of attachment so that the heating depends largely on radiation and convection. Because of this increased efficiency of heat transfer the bonded heaters of the invention can provide adequate heating at substantially less power requirements than do the prior strip heaters. The combination of the flexible heater and the flexible adhesive makes the heater very resistant to shock and vibration from passing trains. It is not necessary to drill the stock -rail at numerous locations for the installation of metal fasteners, as is necessary with the prior art heaters. It is not necessary to grind or mill the switch points or otherwise provide switch points of special shape to insure proper clearances of the heaters. In the event that a heater section becomes inoperative and requires replacement, it is only necessary to remove and reinstall a new length of heating strip rather than the entire heater, as in prior strip heaters. Because the heater is thin as compared to prior strip heaters, it is protected by the head of the rail from damage that might otherwise result from vehicle wheels or dragging or falling equipment.

It is apparent that heaters of this type, comprising one or more strips, may be mounted on the lswitch points either on the side thereof away from the stock rail or on the switch point between the switch point and the stock rail or at other locations than those disclosed on the stock rail or switch point. Those skilled in the art will appreciate that various changes and modifications can be made in the invention without departing from the spirit and `scope thereof. The essential features of the invention are defined in the appended claims.

What is claimed is:

1. In combination, a railroad rail to Ibe heated, and a heater for said railroad rail comprising a flexible heating strip that comprises a plurality of transversely spaced longitudinally extending generally parallel groups of resistance wires embedded in a strip-like body of heatresistant rubber-like material reinforced with glass fiber cloth, said heating strip being bonded to a surface of said railroad rail over essentially the entire heating area of said heating strip by a heat-resistant, heat-conductive, iiexible adhesive, said llexible heating strip closely conforming to said surface of said rail.

2. The apparatus of claim in which said rubber-like material is silicone rubber material.

3. The apparatus of claim 2 in which said adhesive is an air curing adhesive.

4. The apparatus of claim 3 in which said adhesive is silicone rubber adhesive.

5. The apparatus of claim 1 in which said heating strip is mounted on the web of a stock rail of a switch between the stock rail and the switch point, and in which said heater strip is suiiciently thin to clear said point without modilication of the switch point.

6. The apparatus of claim 1 in which there are a plurality of said heating strips connected end-to-end in series relation.

References Cited UNITED STATES PATENTS 1,015,138 1/1912 Cordero 246-428 2,500,399 3/1950 Broome 246-428 2,910,567 10/ 1959 Holstein 246-428 3,243,573 3/1966 Weisse et al. 246--428 OTHER REFERENCES Railway Signaling and Communications, December 1965, p. 37. Copy available in vgroup 317. A copy of page available in class 246/428.

ARTHUR L. LA POINT, Primary Examiner.

R. A. BERTSCH, Assistant Examiner. 

1. IN COMBINATION, A RAILROAD TO BE HEATED, AND A HEATER FOR SAID RAILROAD RAIL COMPRISING A FLEXIBLE HEATING STRIP THAT COMPRISES A PLURALITY OF TRANSVERSELY SPACED LONGITUDINALLY EXTENDING GENERALLY PARALLEL GROUPS OF RESISTANCE WIRES EMBEDDED IN STRIP-LIKE BODY OF HEATRESISTANT RUBBER-LIKE MATERIAL REINFORCED WITH GLASS FIBER CLOTH, SAID HEATING BEING STRIP BONDED TO A SURFACE OF SAID RAILROAD RAIL OVER ESSENTIALLY THE ENTIRE HEATING AREA 